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Amphibian oocytes have many copies of rRNA genes that are actively transcribed. Newt oocyte nuclei were dissected, allowed to swell in a low ionic strength high pH buffer, centrifuged through a sucrose-formaldehyde cushion onto EM grids coated with carbon films, and, in this iamge, stained with aqueous uranly acetate. The strand shows a single rRNA transcript starting at top left and terminating toward the lower right. The tree-like transcribed gene shows closely packed RNA polymerases with inceasingly large nascent rRNA transcripts as they approach the termination point. Nascent transcripts are more compact with negative than positive staining. Nucleosomes are visible in the spacer region at lower right.